The present invention relates to communications in computer networks. More specifically, it relates to a method and system for providing quality-of-service to a cable modem in a data-over-cable system.
Cable television networks such as those provided by Comcast Cable Communications, Inc., of Philadelphia, Pa., Cox Communications of Atlanta Ga., Tele-Communications, Inc., of Englewood Colo. Time-Warner Cable, of Marietta Ga., Continental Cablevision, Inc., of Boston Mass., and others provide cable television services to a large number of subscribers over a large geographical area. The cable television networks typically are interconnected by cables such as coaxial cables or a Hybrid Fiber/Coaxial (xe2x80x9cHFCxe2x80x9d) cable system which have data rates of about 10 Mega-bits-per-second (xe2x80x9cMbpsxe2x80x9d) to 30+ Mbps.
The Internet, a world-wide-network of interconnected computers, provides multi-media content including audio, video, graphics and text that requires a large bandwidth for downloading and viewing. Most Internet Service Providers (xe2x80x9cISPsxe2x80x9d) allow customers to connect to the Internet via a serial telephone line from a Public Switched Telephone Network (xe2x80x9cPSTNxe2x80x9d) at data rates including 14,400 bps, 28,800 bps, 33,600 bps, 56,000 bps and others that are much slower than the about 10 Mbps to 30+ Mbps available on a coaxial cable or HFC cable system on a cable television network.
With the explosive growth of the Internet, many customers have desired to use the larger bandwidth of a cable television network to connect to the Internet and other computer networks. Cable modems, such as those provided by 3Com Corporation of Santa Clara, Calif., Motorola Corporation of Arlington Heights, Ill., Hewlett-Packard Co. of Palo Alto, Calif. Bay Networks of Santa Clara, Ca., Scientific-Atlanta, of Norcross, Ga. and others offer customers higher-speed connectivity to the Internet, an intranet, Local Area Networks (xe2x80x9cLANsxe2x80x9d) and other computer networks via cable television networks. These cable modems currently support a data connection to the Internet and other computer networks via a cable television network with a data rate of up to 30+ Mbps which is a much larger data rate than can be supported by a modem used over a serial telephone line.
However, most cable television networks provide only unidirectional cable systems, supporting only a xe2x80x9cdownstreamxe2x80x9d data path. A downstream data path is the flow of data from a cable system xe2x80x9cheadendxe2x80x9d to a customer. A cable system headend is a central location in the cable television network that is responsible for sending cable signals in the downstream direction. A return data path via a telephone network, such as a public switched telephone network provided by ATandT and others, (i.e., a xe2x80x9ctelephony returnxe2x80x9d) is typically used for an xe2x80x9cupstreamxe2x80x9d data path. An upstream data path is the flow of data from the customer back to the cable system headend. A cable television system with an upstream connection to a telephony network is called a xe2x80x9cdata-over-cable system with telephony return.xe2x80x9d
An exemplary data-over-cable system with telephony return includes customer premise equipment (e.g., a customer computer), a cable modem, a cable modem termination system, a cable television network, a public switched telephone network, a telephony remote access concentrator and a data network (e.g., the Internet). The cable modem termination system and the telephony remote access concentrator together are called a xe2x80x9ctelephony return termination system.xe2x80x9d
The cable modem termination system receives data packets from the data network and transmits them downstream via the cable television network to a cable modem attached to the customer premise equipment. The customer premise equipment sends response data packets to the cable modem, which sends response data packets upstream via public switched telephone network to the telephony remote access concentrator, which sends the response data packets back to the appropriate host on the data network.
When a cable modem used in the data-over-cable system with telephony return is initialized, a connection is made to both the cable modem termination system via the cable network and to the telephony remote access concentrator via the public switched telephone network. As a cable modem is initialized, it will initialize one or more downstream channels (i.e., downstream connections) to the cable modem termination system via the cable network or the telephony remote access concentrator via the public switched telephone network.
As a cable modem is initialized in a data-over-cable system, it registers with a cable modem termination system to allow the cable modem to receive data over a cable television connection and from a data network (e.g., the Internet or an Intranet). The cable modem forwards configuration information it receives in a configuration file during initialization to the cable modem termination system as part of a registration request message.
Configuration information forwarded to a cable modem termination system from a cable modem includes Class-of-Service (xe2x80x9cCoSxe2x80x9d) and Quality-of-Service (xe2x80x9cQoSxe2x80x9d) and other parameters. As is known in the art, class-of-service provides a reliable (e.g., error free, in sequence, with no loss of duplication) transport facility independent of the quality-of-service. Class-of-service parameters include maximum downstream data rates, maximum upstream data rates, upstream channel priority, guaranteed minimum data rates, guaranteed maximum data rate and other parameters. Quality-of-service collectively specifies the performance of a network service that a device expects on a network. Quality-of-service parameters include transit delay expected to deliver data to a specific destination, the level of protection from unauthorized monitoring or modification of data, cost for delivery of data, expected residual error probability, the relative priority associated with the data and other parameters.
A cable modem termination system is responsible for providing class-of-service and quality-of-service connections to a cable modem. However, there are several problems associated with using a cable modem termination system to provide class-of-service and quality-of-service connections to a cable modem. The cable modem termination system is responsible for handling and balancing class-of-service and quality-of-service requests for tens of thousands of cable modems. The handling and balancing class-of-service and quality-of-service includes allocating bandwidth for guaranteed transmission rates requested by the cable modems. The handling and balancing requires significant computational and computer resources on the cable modem termination system. The cable modem termination system uses complex software that is not easily adaptable to new or additional class-of-service or quality-of-service parameters. In addition, multiple cable modem termination systems in a data-over-cable systems do not handle or balance class-of-service or quality-of-service parameters in a standard way. Thus, it is desirable to provide a standard, efficient and cost effective way to provide class-of-service and quality-of-service to cable modems in a data-over-cable system.
In accordance with a preferred embodiment of the present invention, the problems associated with providing quality-of-service to a cable modem in a data-over-cable system are overcome. A system and method for providing quality of service to a cable modem in a data-over-cable system is provided.
The system includes a quality-of-service server, for determining whether a first network device has enough available bandwidth to establish a connection to a second network device with a specific quality-of-service requested by the second network device. The quality-of-service server provides support for class-of-service, quality-of-service and other parameters. The system also includes multiple quality-of-service identifiers, for identifying a transmission bandwidth required for a specific quality-of-service requested by a second network device, wherein a value for a quality-of-service identifier is determined by the quality-of-service bandwidth requested by class-of-service, quality-of-service and other parameters.
In a preferred embodiment of the present invention, the first network device is a cable modem termination system and the second network device is a cable modem. However, the present invention is not limited to these network devices and other network devices could also be used.
The method includes receiving a request on a first network device from a second network device to establish a connection between the second network device and a third network device with a specific quality-of-service requested by the third network device. The first network device determines whether the second network device has enough available bandwidth to establish the connection to the third network device with the specific quality-of-service requested by the third network device. The quality-of-service request includes class-of-service and quality-of-service parameters. If the first network device has enough bandwidth to establish the connection to the third network device with the specific quality-of-service desired by the third network device, a bandwidth required for the specific quality-of-service requested by the third network device is subtracted from an available bandwidth for the second network device. The bandwidth required includes bandwidth for the requested class-of-service and quality-of-service parameters. A quality-of-service identifier is assigned to the specific quality-of-service bandwidth requested by the third network device. The assigned quality-of-service identifier is saved on the first network device. The assigned quality-of-service identifier is sent to the second network device indicating the second network device has enough bandwidth to allow the connection with the specific quality-of-service requested by the third network device.
In a preferred embodiment of the present invention, the first network device is a quality-of-service server, the second network device is a cable modem termination system and the third network device is a cable modem. The quality-of-service server provides support for quality-of-service, class-of-service, and other parameters, but is called a xe2x80x9cquality-of-service serverxe2x80x9d for the sake of simplicity. However, the present invention is not limited to these network devices and other network devices could also be used.
A preferred embodiment of the present invention offers several advantages over the prior art. A preferred embodiment of the present invention allows class-of-service and quality-of-service to be handled and balanced in a data-over-cable system by a quality-of-service server. This relieves the computational burden from the cable modem termination system and helps reduce or eliminate the need for complex class-of-service and quality-of-service software on the cable modem termination system. The class-of-service server provides a standardized way of handling class-of-service and quality-of-service requests and is easily adaptable for new class-of-service or quality-of-service parameters.